Delivery of cells to the myocardium has shown promise for the treatment of heart failure patients. The specific cell type or types which will be most effective as treatment are currently under study.
Recently, implantation of the bone marrow mononuclear cell fraction to the ischemic heart has resulted in positive histological and functional cardiac improvement. (Kamihata H. et al. Circulation 2001; 104(9):1046-1052) However, the mononuclear cell fraction contains cell types other than stem and progenitor cells, e.g., monocytes and lymphocytes, potentially resulting in lower effectiveness and increased inflammatory response. More specific selection methods, e.g., isolation of stem cells which only express the stem cell marker CD34+, leave out some of the most primitive stem cells. (Dao MA and Nolta JA Leukemia 2000; 14:773-776) Other recent studies have determined that local injection of lineage negative c-kit+ bone marrow cells from transgenic mice expressing enhanced green fluorescent protein into the contracting wall bordering infarcted myocardium resulted in myocardial regeneration, wherein the developing tissue comprised proliferating myocytes and vascular structures. (Orlic D. et al. Nature 2001; 401(6829):701-705)
Other recent studies have determined that local injection of lineage negative c-kitPOS bone marrow cells from transgenic mice expressing enhanced green fluorescent protein into the contracting wall bordering infarcted myocardium resulted in myocardial regeneration, wherein the developing tissue comprised proliferating myocytes and vascular structures. (Orlic D. et al. Nature 2001; 401(6829):701-705)
Additional investigations have found that transplantation of highly enriched adult hematopoietic stem cells, called side population (SP) cells into lethally irradiated mice subsequently rendered ischemic by coronary artery occlusion followed by reperfusion resulted in migration of SP cells (CD34−/low, c-kit+, Sca+) or their progeny into ischemic cardiac muscle and blood vessels, differentiation to cardiomyocytes and endothelial cells, and contribution to the formation of functional tissue. (Jackson K. A. et al. J. Clin. Investig. 2001 107(11):1395-1402) The SP cells were selected by lack of nuclear staining with Hoechst dye and were additionally tested for c-Kit expression and PECAM-1 (CD31) expression. (Jackson K. A. et al. J. Clin. Investig. 2001)
Therefore, delivery of all lineage negative (Lin−) mononuclear cells, i.e., cells which do not exhibit phenotypic characteristics of any committed or terminally differentiated cell type, or the side population (SP) cells subset of the Lin− mononuclear cells, will conserve all relevant stem cells and obviate the current use of additional specific selection methods.
Accordingly, the present invention discloses that transplantation of autologous lineage negative (Lin−) mononuclear cells or side population (SP) cells, which is a subset of cells within the Lin− mononuclear cell population or which may be isolated from other organs such as skeletal muscle, cardiac muscle, liver and kidney, directly into or adjacent to diseased or injured tissue, e.g., the myocardium, results in engraftment of the transplanted Lin− mononuclear cells or side population cells, their differentiation into cardiomyocytes and/or endothelial cells, and formation of functional tissue. The use of Lin− mononuclear cells, or alternatively, SP cells, maintains a therapeutically valuable population of stem and progenitors by excluding differentiated and committed cell types without unnecessary additional processing for identification of specific stem cell markers.
Isolation of autologous lineage negative mononuclear cells or side population cells from the bone marrow (Lin− BM-MNCs) or peripheral blood containing uncommitted or undifferentiated mononuclear cells (Lin− MNCs) or isolation of side population (SP) cells from nonhematopoietic tissues and the direct delivery of such Lin− mononuclear cells or side population cells to tissues such as the myocardium or coronary blood vessels, as provided by the present invention, is a novel therapeutic strategy for heart failure in adult mammals. Such a strategy is also useful for treatment of other types of tissue in need of neovascularization, e.g., skeletal muscle.